1. Field of the Invention
The present invention relates to a layered-type piezoelectric element provided in an ink jet print head which ejects ink droplets to produce diagrams or characters by dots on a print medium and to a method for producing the layered-type piezoelectric element.
2. Description of the Related Art
Conventionally, there has been know an ink jet print head including piezoelectric elements. Each piezoelectric element either forms or is attached to a wall surface defining an ink reservoir or ink channel. When one of the piezoelectric elements is applied with a voltage, the piezoelectric element deforms, causing a displacement which changes the volume of the corresponding ink channel. Increase in pressure accompanying the volume change ejects an ink droplet from a nozzle fluidly connected with the ink channel.
Japanese Patent Application (Kokai) No. HEI-6-79871 discloses a configuration typical for such an ink jet print head. As shown in FIG. 1, vertically-displacing pillar-shaped piezoelectric ceramic elements 81 serving as layered-type actuators are formed from a block-shaped cintered body into which elongated grooves have been opened with a slicer or other instrument. The piezoelectric ceramic elements 81 are configured from stacks of thin piezoelectric element sheets alternating with thin internal electrodes. This configuration allows low voltage drive of the piezoelectric ceramic elements 81. The internal electrodes are exposed in alternation at opposing side surfaces of the piezoelectric ceramic elements 81. The internal electrodes are connected, by wire bonding or by other means, to a drive power source for supplying a voltage for driving the piezoelectric ceramic elements 81.
An elastic thin plate 82 is adhered to the tip ends of the pillar-shaped piezoelectric ceramic elements 81. Further, a nozzle plate 84 made from resin and formed with ink channels 83 and nozzles 83a is adhered to the thin plate 82 so that tip ends of the piezoelectric ceramic elements 81 are positioned over corresponding ink channels 83. Application of a voltage to the piezoelectric ceramic elements 81 produces displacement which deforms the thin plate 82 and ejects ink in the ink channel 83 from the nozzles 83a. Dot-pattern characters and other images can therefore be printed.
However, the pillar-shaped piezoelectric ceramic elements 81 of the ink jet print head shown in FIG. 7 easily break because they are thin independent units. Because the pillar-shaped piezoelectric ceramic elements 81 break easily, production yield of the ink jet print head is low. Also, the ink jet print head is unreliable because the pillar-shaped piezoelectric ceramic elements 81 can easily break when driven.
Also, producing the piezoelectric ceramic elements 81 requires many production processes such as machining the pillar-shaped piezoelectric element using a slicer and such as wire bonding for the power supply. The great number of production processes makes the piezoelectric ceramic elements 81 expensive to produce.